In a wiping device of a conventional intaglio printing press, a wiping roller is thermally expanded by the heat generated by the rotation of the printing press, which increases the nip pressure between an intaglio cylinder and the wiping roller. As a result, the wear of the surface of the wiping roller is abnormally increased, thereby shortening the life of the wiping roller. Moreover, ink adhering to the intaglio cylinder is excessively wiped off, thereby making it impossible to obtain proper printing products.
For this reason, the operator must firstly manually adjust the nip pressure between the intaglio cylinder and the wiping roller by checking printing products printed in test printing in a printing preparation phase, which involves low-speed rotation; then, after the speed is raised to a printing speed and the printing press reaches a heat generating state, the operator must manually adjust the nip pressure again by checking the conditions of printing products printed in final printing. This has been a first problem and caused a burden on the operator and also produced a large amount of defective printing products and wasted printing materials due to the manual adjustment from the beginning.
Also, in the wiping device of the conventional intaglio printing press, the wiping roller is brought into pressure contact with the intaglio cylinder and further is rotated in the opposite direction to wipe excess ink off the intaglio cylinder at the contacting portion. Thus, the rubber at the surface of the wiping roller gradually wears.
For this reason, the operator moves the position of the axis of the wiping roller closer to the axis of the intaglio cylinder by the amount of the wear to adjust and maintain the appropriate contact pressure between the intaglio cylinder and the wiping roller so that proper printing products can always be obtained.
Then, the larger the wear becomes, that is, the longer the time passes, the closer the axis of the wiping roller gets to the axis of the intaglio cylinder.
Thus, when the wiping roller wears out and becomes no longer able to properly wipe off ink, the wiping roller is replaced with a new wiping roller.
Here, the axis of the wiping roller has been moved closer to the axis of the intaglio cylinder by the amount of the wear. Thus, if printing is started in such a state, the wear of the surface of the wiping roller will be abnormally large, thereby shortening the life of the wiping roller. Moreover, ink adhering to the intaglio cylinder will be excessively wiped off, thereby making it impossible to obtain proper printing products.
For this reason, the operator must manually adjust the nip pressure between the intaglio cylinder and the wiping roller again by checking printing products printed in test printing or final printing. This has been a second problem and caused a burden on the operator and also produced a large amount of defective printing products and wasted printing materials due to the manual adjustment from the beginning.
In this connection, Patent Document 1 (Japanese Patent Application Publication No. 2011-251504) has proposed a method which includes measuring load applied to a wiping-roller drive motor (the value of current flowing through the motor) configured to drive a wiping roller, and performing control such that this value will be a reference value.
However, the control of Patent Document 1 is complicated and takes time, effort, and cost to incorporate into a machine, and it is therefore frequently the case that the operator still performs manual adjustment.